Patient interfaces typically include a rigid shell or frame and a soft face-contacting cushion. The cushion spaces the frame away from the patient's face. The frame and cushion define a cavity which receives the patient's nose or nose and mouth. The frame and cushion are held in position on the patient's face by a headgear assembly.
A known patient interface, commercially sold under the name of Activa® by ResMed Ltd., includes a cushion having a gusset portion. Further details and embodiments of this cushion are disclosed in U.S. patent application Ser. No. 10/655,622, filed Sep. 5, 2003, the entirety of which is hereby incorporated herein by reference.
The gusset portion is positioned between the frame-contacting side and the face-contacting side of the cushion. In one embodiment described in the application, a reinforcing ring is provided between the gusset portion and the face-contacting side. The reinforcing ring acts as a stiffening hoop reducing the tendency of the cushion to expand at that point when under pressure. In one form, the reinforcing ring is made from polycarbonate and is overmolded or push-fit.
A need in the art has developed to provide improvements to the above-described reinforcing ring to limit expansion of the cushion when under pressure.